The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
A synchronizer which is mainly used in a multi-ratio transmission is configured to selectively couple any one of two driving gears, which are running idle on an outer circumferential surface of a major shaft, to the major shaft and synchronize the major shaft with a rotating speed of the selected driving gear to reduce a shifting shock.
FIG. 1 is an exemplified diagram of a synchronizer 10 and a shift mechanism 20 connected to the synchronizer 10 to move the synchronizer 10.
The major shaft 1 to which power is delivered is installed in the synchronizer 10 and both ends of the synchronizer 10 are each provided with first and second clutch gears 18 and 19, in which each of the clutch gears 18 and 19 are integrally formed in each driving gear (not illustrated) and both ends of the synchronizer 10 are provided with two driving gears. A gear combination of the two driving gears, for example, may include one shift and two shift driving gears, or one shift and three shift driving gears, etc.
The synchronizer 10 includes a hub 11 connected to an outer circumferential surface of the major shaft 1 through a spline, etc., a sleeve 12 configured to move along a longitudinal direction (left and right on the page of FIG. 1, shown by phantom line) of the major shaft 1 while engaging with an outer circumferential surface of the hub 11 through a spline, etc., a key unit 13 provided on the outer circumferential surface of the hub 11 and configured to contact an inner circumferential surface of the sleeve 12, and first and second rings 14 and 15 provided on both surfaces of the hub 11.
The shift mechanism 20 includes an actuator 21, a finger 22 protruding radially from an output shaft of the actuator 21, a lug 23 into which the finger 22 is inserted, a shift fork 24 extending from the lug 23 to the sleeve 12 of the synchronizer 10, a shift rail 25 extending in a length direction from one side of the shift fork 24, etc.
The lug 23 is provided with a groove part 23a and the finger 22 is coupled with the groove part 23a of the lug 23.
The outer circumferential surface of the sleeve 12 is provided with the groove part 12a, and a lower end of the shift fork 24 is inserted into the groove part 12a of the sleeve 12.
The shift rail 25 is provided with a plurality of locking grooves 25a, 25b, and 25c and the locking grooves 25a, 25b, and 25c of the shift rail 25 are configured to selectively lock a plug 26 according to corresponding shift stages.
As the shift fork 24 horizontally moves along the longitudinal direction of the major shaft 1 through the finger 22 and the lug 23 of the actuator 21, the ring 14 of the synchronizer 10 is pressed to any one of the first and second clutch gears 18 and 19 to engage the sleeve 12 of the synchronizer 10 with the corresponding clutch gears 18 and 19 and couple the driving gears of the corresponding clutch gears 18 and 19 with the major shaft 1, such that the rotating speed of the sleeve 12 of the synchronizer 10 may synchronize with the rotating speed of corresponding driving gear.
Further, when the synchronizer 10 moves to a neutral position, a contact of the synchronizer 10 with the first and second clutch gears 18 and 19 may be released, and preferably completely out of contact.
Meanwhile, it has been discovered that, a first clearance t1 formed between the finger 22 and the groove part 23a of the lug 23 and a second clearance t2 formed between the shift fork 24 and the groove part 12a of the sleeve 12, which are provided to make the driving of the shift mechanism 20 more smooth, can act as an invalid stroke at the time of the movement of the sleeve 12 and the finger 22.
When the invalid stroke occurs due to the first and second clearances t1 and t2 at the time of the neutral control of the synchronizer 10, the sleeve 12 and the finger 22 of the synchronizer 10 are biased to any one side, and therefore the key unit 13 may not be positioned at a center between the two rings 14 and 15.
As such, when the key unit 13 is not positioned at the center between the first and second rings 14 and 15 but is biased to one side, the key unit 13 of the synchronizer 10 contacts any one of the rings 14 and 15 or is not properly spaced apart the rings and therefore a burning damage of the rings 14 and 15 occurs or an interval between the key unit 13 and the rings 14 and 15 is not secured properly while a vehicle is driving to cause a friction and a drag, such that fuel efficiency may be greatly aggravated.